Distillation process using microchannel technology

Abstract

The disclosed invention relates to a distillation process for separating two or more components having different volatilities from a liquid mixture containing the components. The process employs microchannel technology for effecting the distillation and is particularly suitable for conducting difficult separations, such as the separation of ethane from ethylene, wherein the individual components are characterized by having volatilities that are very close to one another.

1 . A process for distilling a fluid mixture in a microchannel distillation unit, the microchannel distillation unit comprising a plurality of microchannel distillation sections, a distillate end and a microchannel condenser at the distillate end, a bottoms end and a microchannel reboiler at the bottoms end, and at least one feed inlet, the fluid mixture comprising a more volatile component and a less volatile component, the process comprising:
 flowing the fluid mixture through the at least one feed inlet into at least one microchannel distillation section, part of the more volatile component transferring from the fluid mixture to the vapor phase to form a more volatile component rich vapor phase, part of the less volatile component transferring from the fluid mixture to the liquid phase to form a less volatile component rich liquid phase;   flowing the more volatile component rich vapor phase through at least one of the microchannel distillation sections towards the distillate end, the more volatile component rich vapor phase contacting the liquid phase in each microchannel distillation section and becoming enriched with the more volatile component;   condensing at least part of the more volatile component rich vapor phase in the microchannel condenser and withdrawing at least part of the condensed more volatile component rich vapor phase from the microchannel distillation unit;   flowing the less volatile component rich liquid phase through at least one of the microchannel distillation sections towards the bottoms end, the less volatile component rich liquid phase contacting the vapor phase in each microchannel distillation section and becoming enriched with the less volatile component; and   vaporizing at least part of the less volatile component rich liquid phase in the microchannel reboiler and flowing at least part of the vaporized less volatile component rich liquid phase back into the microchannel distillation unit.   
   
   
       2 . The process of  claim 1  wherein at least part of the more volatile component rich vapor phase is condensed in the microchannel condenser and flows back into the microchannel distillation unit. 
   
   
       3 . The process of  claim 1  wherein at least part of the less volatile component rich liquid phase is withdrawn from the microchannel distillation unit. 
   
   
       4 . The process of  claim 1  wherein the microchannel distillation unit is in a microchannel distillation assembly comprising a plurality of microchannel distillation units, some of the microchannel distillation units being active and some of the microchannel distillation units being inactive. 
   
   
       5 . The process of  claim 1  wherein each microchannel distillation unit has a height of up to about 3 meters. 
   
   
       6 . The process of  claim 1  wherein the at least one feed inlet is positioned between the distillate end and the bottoms end. 
   
   
       7 . The process of  claim 1  wherein the microchannel distillation unit further comprises one or more heat exchange zones thermally communicating with the microchannel distillation unit. 
   
   
       8 . The process of  claim 7  wherein each heat exchange zone comprises at least one heat exchange channel. 
   
   
       9 . The process of  claim 7  wherein each heat exchange zone comprises at least one heat exchange fluid loop, a heat exchange fluid flowing from one heat exchange fluid loop to another heat exchange fluid loop. 
   
   
       10 . The process of  claim 9  wherein at least two heat exchange fluid loops are nested. 
   
   
       11 . The process of  claim 7  wherein each heat exchange zone comprises one or more heat exchange channels, a heat exchange fluid flowing in the heat exchange channels, the heat exchange fluid flowing in a direction that is co-current, cross-current or counter current relative to the flow of the more volatile component rich vapor phase in the microchannel distillation unit. 
   
   
       12 . The process of  claim 7  wherein a heat exchange fluid flows in the one or more heat exchange zones, the heat exchange fluid undergoing partial boiling in the heat exchange zones, the pressure of the heat exchange fluid in each of the heat exchange zones being different. 
   
   
       13 . The process of  claim 7  wherein a heat exchange fluid flows in the heat exchange zones, the heat exchange fluid undergoing partial boiling in the heat exchange zones, the temperature in each microchannel distillation section being different. 
   
   
       14 . The process of  claim 7  wherein a heat exchange fluid flows in the one or more heat exchange zone, the heat exchange fluid comprising one or more of air, steam, liquid water, carbon dioxide, gaseous nitrogen, liquid nitrogen, a gaseous hydrocarbon or a liquid hydrocarbon. 
   
   
       15 . The process of  claim 7  wherein each microchannel distillation section is operated at a different temperature. 
   
   
       16 . The process of  claim 7  wherein an endothermic or exothermic process is conducted in one or more of the heat exchange zones. 
   
   
       17 . A process for separating a first fluid from a fluid mixture comprising the first fluid and a second fluid, the process being conducted in a microchannel distillation unit comprising a plurality of distillation microchannels, the process comprising: contacting a vapor phase of the fluid mixture with a liquid phase of the fluid mixture in the distillation microchannels, enriching the vapor phase with the first fluid to form a distillate product, and flowing the distillate product out of the microchannel distillation unit, the height of an equivalent theoretical plate ratio for the microchannel distillation unit being less than about 6 inches, the distillate product comprising a first fluid content of at least about 95% by volume. 
   
   
       18 . The process of  claim 17  wherein the process comprises separating ethylene from ethane. 
   
   
       19 . The process of  claim 17  wherein the process comprises separating styrene from ethylbenzene. 
   
   
       20 . The process of  claim 17  wherein the process comprises separating oxygen from nitrogen. 
   
   
       21 . The process of  claim 17  wherein the process comprises separating cyclohexane from cyclohexanol or cyclohexanone. 
   
   
       22 . The process of  claim 17  wherein the process comprises separating hexane from cyclohexane. 
   
   
       23 . The process of  claim 17  wherein the fluid mixture comprises isobutane. 
   
   
       24 . The process of  claim 17  wherein the fluid mixture comprises naptha. 
   
   
       25 . The process of  claim 16  wherein the pressure in the microchannel distillation unit is in the range from about 30 to about 100 atmospheres. 
   
   
       26 . A process for separating a first fluid from a fluid mixture comprising the first fluid and a second fluid, the process being conducted in a microchannel distillation unit comprising a plurality of distillation microchannels, the process comprising: contacting a vapor phase of the fluid mixture with a liquid phase of the fluid mixture in one or more of the distillation microchannels, enriching the vapor phase with the first fluid to form a distillate product, and flowing the distillate product out of the microchannel distillation unit, the process exhibiting a fast response to a step change in the feed rate of the fluid mixture into the microchannel distillation unit or to a step change in the mole fraction of the component of the fluid mixture having the largest mole fraction in the fluid mixture entering the microchannel distillation unit prior to the step change. 
   
   
       27 . A process for separating a first fluid from a fluid mixture comprising the first fluid and a second fluid, the process being conducted in a first microchannel distillation unit and a second microchannel distillation unit, each microchannel distillation unit comprising a plurality of distillation microchannels, the process comprising: contacting a vapor phase of the fluid mixture with a liquid phase of the fluid mixture in one or more of the distillation microchannels in the first microchannel distillation unit, enriching the vapor phase with the first fluid to form a first distillate product; flowing the first distillate product from the first microchannel distillation unit into the second microchannel distillation unit; contacting a vapor phase of the first distillate product with a liquid phase of the first distillate product in one or more of the distillation microchannels in the second microchannel distillation unit; enriching the first distillate product with the first fluid to form a second distillate product; and flowing the second distillate product out of the second microchannel distillation unit.